Dutch coffee shops barred from selling 'strong' or 'skunk' cannabis, Coffee shops in the Netherlands were left wondering on Saturday how to comply with restrictions announced by the Dutch government on the sale of "strong" cannabis, saying enforcement would be difficult given the laws on production.Dutch coffee shops. The Netherlands is famous for its liberal soft drugs policies. A Dutch citizen can grow a maximum of five cannabis plants at home for personal use but large-scale production and transport is a crime.

On Friday, the coalition government said it would seek to ban what it considered to be highly potent forms of cannabis -- known as "skunk" -- placing them in the same category as hard drugs such as heroin or cocaine.

But the industry said the guidelines were not clear enough.

"Commercial cannabis growers are already breaking the law so how can testing be legal? It's not clear what coffee shops need to do," said Maurice Veldman, a lawyer from the Dutch cannabis retailers association who represents coffee shops in court.

A pioneer of liberal drug policies, the Netherlands has backtracked on its tolerance in the last few years, announcing plans in May to ban tourists from coffee shops, which are popular attractions in cities such as Amsterdam.

The government said it would now outlaw the sale of cannabis whose concentration of THC, seen as the main psychoactive substance, exceeds 15 percent.

The average THC concentration in cannabis sold by Dutch coffee shops is between 16 and 18 percent, according to the Trimbos Institute.

"All this will do is lead to people smoking more joints and me selling more grams. But as it's used with tobacco it will damage their health more," said Marc Josemans, who owns a coffee shop in the city of Maastricht.

The Dutch government says high THC content is detrimental to mental health, particularly when used at a young age, and that it wants to send a clear signal that strong cannabis poses an unacceptable risk to users.